1. Technical Field
This invention relates generally to the field of catheterization, and more specifically to new apparatus and method for facilitating balloon catheter exchange during dilatation procedures such as angioplasty.
2. Background Art
Catheterization procedures are well known for diagnosis and therapy of lesions in the cardiovascular system. One such procedure is angioplasty, for eliminating or ameliorating the vascular plaque blockage or constriction in blood vessels associated with the provision of the heart's blood supply. In an angioplasty procedure, an expandable balloon carried by an elongated catheter is introduced into the patient's arterial system and advanced until it is positioned in the region of the blockage or constriction. Once so positioned, the balloon is expanded by filling it with a liquid. In successful procedures, the expandable balloon presses outwardly against the walls of the artery and expands the artery to a degree to which the artery is either partially or totally re-opened to blood flow.
A typical angioplasty procedure for opening the coronary artery and components used in practicing the illustrative procedure, are now described.
Prior to initiating the angioplasty procedure, a guiding catheter is placed typically via the femoral artery into the aorta and its tip is engaged into the coronary arteries which branch from the aorta. This entrance into the coronary artery is called the osteum. Once placed, the guiding catheter acts as a conduit to access the coronary arteries with a guidewire and balloon catheter. The guiding catheter is a portion of plastic tubing having a length of about 95 centimeters, an inside diameter of about 0.08 inches, and an outside diameter of about 2.5 millimeters.
The physician threads a balloon catheter onto a guidewire. This operation takes place external to the patient.
The guidewire is a piece of stainless steel and platinum wire, approximately 175 centimeters in length, and about 0.010-0.018 inches in diameter. The soft distal tip of the guidewire can be shaped to form a "J" configuration. This "J" shape allows the physician to steer the wire by twisting the proximal extremity of the wire while advancing or retracting the wire.
The balloon catheter is an elongated flexible plastic member defining two longitudinal passages and having a balloon located near its distal end. One longitudinal opening defines a sleeve through which the guidewire can be passed. The other longitudinal passage defines a conduit communicating with the interior of the balloon and through which inflation fluid can be injected to inflate the balloon.
Among the types of balloon catheters is one of a type in which the two longitudinal passages are generally side by side and parallel. In another type of balloon catheter, the two longitudinal passages are co-axial. In this latter type, the balloon guidewire is passed down the inner passage and the inflation fluid is injected into the balloon via the outer passage.
Balloon catheters, as well as associated apparatus and method for use in angioplasty, are described in U.S. Pat. No. 5,040,548, issued on Aug. 20, 1991, to Yock, and U.S. Pat. No. 4,762,129, issued on Aug. 8, 1988. Each of these issued U.S. patents is hereby expressly incorporated by reference.
The physician passes the guidewire through the appropriate one of the longitudinal passages in the balloon catheter, leaving a portion of the guidewire extending from the distal end of the balloon catheter and also a portion extending from its proximal end.
This assembly is then inserted into the proximal end of the guiding catheter, distal end first. The assembly is inserted until the balloon which is attached near the distal end of the balloon catheter is near the distal end of the guiding catheter. At this point, the physician, while maintaining the balloon catheter stationary, pushes on the balloon guidewire to advance it outwardly from the distal end of the guiding catheter.
The guidewire can be steered by appropriate twisting movement by the physician.
The physician steers the guidewire into the chosen one of the coronary arteries, and advances it until it reaches a location of constriction which the physician desires to re-open. Carefully, the physician eases the guidewire's distal end through the region of restriction until the guidewire tip is on the opposite side of the constriction, relative to the guiding catheter.
With the guidewire held stationary, the physician then advances the balloon catheter. The distal end of the balloon catheter, as it is advanced, will, of course, follow the balloon guidewire which is already in place.
The physician continues to advance the balloon until it is located in the region of constriction of the artery. With the balloon and its associated catheter held stationary, inflation fluid is injected into the conduit which communicates with the balloon, causing it to inflate. Inflation of the balloon expands the walls of the artery in the region of constriction and, in successful procedures, re-opens the artery to sufficient blood flow.
Arteries vary in size, and therefore balloon catheters having balloons of different sizes are provided for the physician's selection. These balloons, when inflated, range from about 1.5 millimeters to about 4 millimeters in diameter.
Sometimes, it is necessary for the physician to use more than one balloon to open an artery. Sometimes, the chosen balloon is too large to be advanced into the constricted area. In other instances, the first chosen balloon size, even when inflated, is not large enough to open the constricted area to the degree desired. In such cases, it is necessary to exchange one balloon for another during the same angioplasty procedure.
In order to accomplish this exchange, the guidewire is left in place, and the balloon catheter is withdrawn entirely from the guiding catheter until it is completely disengaged from the proximal end of the guidewire. A new balloon catheter, having a different sized balloon, is then re-inserted over the balloon guidewire and advanced back to the location of the constricted area, where it is used to effect the desired result.
Once the guidewire is initially in place, extending past the constricted area, it is highly desirable to leave the balloon guidewire in place for the entirety of the duration of the angioplasty procedure. This means that the balloon guidewire must remain in place even during exchanges of balloons. The reason for this is that, when a foreign object, such as the balloon guidewire, is introduced into an artery, the artery walls sometimes go into spasm, and constrict generally along a substantial portion of its length. If the artery tends to contract in this way, removal of the balloon guidewire while the artery is so contracted will sometimes render it virtually impossible to re-insert the guidewire through the contracted artery.
Withdrawal of the balloon catheter, while preventing movement of the balloon guidewire, is a difficult and cumbersome procedure, requiring both a second individual, in addition to the physician, and the attachment of a removable extension to the proximal end of the guidewire.
Attachment of the extension to the guidewire during withdrawal of the balloon catheter is necessary because, if the balloon catheter were withdrawn over the proximal end of the guidewire, there would be no way that the guidewire could be manually held stationary. Attachment of the extension to the proximal end of the guidewire extends the guidewire to a point at which the proximal end of the extension still extends outwardly from the proximal end of the balloon catheter even when the balloon catheter is entirely withdrawn from the patient.
Even with the extension, the physician must enlist the aid of an assistant to manually hold stationary the end of the guidewire, preventing guidewire movement, while the physician withdraws the balloon catheter. This is a cumbersome and awkward procedure at best.
It is a general object of the present invention to provide apparatus and method for facilitating introduction and exchange of balloons in angioplasty procedures without the need for manually holding the guidewire in place.